Not long before an explosion that she doesn't see coming, a CIA operative in Kathryn Bigelow's extraordinary "Zero Dark Thirty" offers a toast.

"To big breaks, and the little people who make them happen."

With an astute, beat-perfect sense of storytelling and character, Bigelow and screenwriter Mark Boal shape history -- those breaks, big and small, that led to the killing of Osama bin Laden -- into one of the finest fact-based thrillers since "All the President's Men."

Culled from public sources and original reportage, "Zero" surpasses in scope, ambition and showmanship the filmmaking duo's 2009 Oscar-winning "The Hurt Locker."

It is, by a safe margin, the best movie of the year.

And by an even larger margin, the most controversial.

The film's explicit depiction of torture -- a comparatively brief part of the movie -- has been interpreted by some pundits as an endorsement.

The New York Times columnist Frank Bruni even suggested that Dick Cheney will love "Zero Dark Thirty."

Perhaps. But only if the former Vice-President watches with ideological blinders.

9/11 revisited

Opening with audiotapes of emergency calls from the World Trade Center inferno played over a black screen, "Zero Dark Thirty" (military speak for 12:30 a.m., or deep night) plunges us directly into that day's ever retrievable mindset of panic and grief.

From there, we're in Pakistan, specifically a CIA black site warehouse. A newly arrived agent named Maya (Jessica Chastain, setting the pace for an excellent cast) is observing, up close, the torture of a suspected al-Qaida moneyman named Ammar (Reda Kateb).

This is graphic, ugly stuff. Chained from the ceiling, the bruised and bloodied Ammar is beaten, sexually humiliated, waterboarded and finally stuffed into a small box, his body contorted and smeared with his own excrement, his stench mocked.

Ammar does indeed spill a secret, but only during a relatively calm lunch, and he's tricked, not tortured, into the revelation.

Elsewhere in the film, torture produces false information, and a crucial breakthrough (no spoilers here) arrives after an agent gripes to his boss about post-Obama restrictions on detainee treatment.

"You'll think of something," the boss says.

After Ammar's initial tip, Maya (reportedly based on a real agent, possibly the same one who inspired Claire Danes's Carrie in "Homeland") develops the hunch that we know will pay off: Find bin Laden's courier, and she'll find bin Laden.

As her determination intensifies (particularly after losing a colleague, winningly played by Jennifer Ehle, in the 2009 suicide bombing of a CIA base in Afghanistan), the country's political will to kill bin Laden dissipates.

Among the paternalistic, politically-minded agency heads (portrayed by Kyle Chandler, Mark Strong and James Gandolfini as the here-unnamed CIA director Leon Panetta), Maya is more tolerated than encouraged.

Secret compound

"Zero" adheres to the now familiar manhunt narrative, with satellite images and various clues leading inexorably to bin Laden's compound in Jordan (recreated in exacting detail by production designer Jeremy Hindle).

As good as the film has been to this point, "Zero" hits overdrive in its final extended sequence, when Maya's storyline gives way to the Navy SEAL's raid on the Abbottabad compound.

In several quick, pre-raid scenes, Bigelow and Boal efficiently sketch out a few SEAL Team characters (actors Joel Edgerton and Chris Pratt, in particular, make vivid impressions).

The raid itself is first-class filmmaking, from the eerily quiet stealth helicopters low-flying through mountain passes to the tense room-by-room search.

Shot by cinematographer Greig Fraser in greenish night vision and the occasional glare of explosions, flashlights and lasers, the raid plays out in what feels like real time.

Night shots

As perspectives shift, we see both the SEALs and what the SEALs see. Various inhabitants of the compound, armed and unarmed, male and female, are shot (and shot again) until bin Laden himself is assassinated (and, in this telling, there can be no other word for it).

"Zero Dark Thirty" gives Maya the last word, leaving both the film and the character irrevocably wrenched by the interrogator's credo: In the end, everybody breaks.

"Zero Dark Thirty," from Columbia Pictures, is playing in New York and Los Angeles, opening nationwide January 11. Rating: *****